1. Field of the Invention
The present invention relates to vacuum processing methods and, more particularly, to vacuum processing methods of carrying out some processing of an article in a reaction vessel (or container) kept in a pressure-reduced state. More specifically, the invention concerns methods of subjecting an article in a reaction vessel kept in a pressure-reduced state to such processing as deposited film formation, etching, and so on, which is used in steps of producing semiconductor devices, photosensitive members for electrophotography, line sensors for image inputting, image pickup devices, photovoltaic devices, and so on. Further, the invention relates to methods of producing the semiconductor devices, photosensitive members for electrophotography, line sensors for image inputting, image pickup devices, photovoltaic devices, etc. by making use of the aforementioned vacuum processing method in steps thereof.
2. Related Background Art
Conventionally, a number of methods are known as vacuum processing methods used in the steps of producing the semiconductor devices, photosensitive members for electrophotography, line sensors for image inputting, image pickup devices, photovoltaic devices, other various electronic devices, optical elements, and so on; e.g., vacuum evaporation, sputtering, ion plating, thermal CVD, photo CVD, plasma CVD, plasma etching, and so on. In addition, systems for carrying out the methods are also put into practical use.
For example, the plasma CVD methods, i.e., methods of decomposing a source gas by a dc or high frequency or microwave glow discharge to form a thin deposited film on a substrate, are practically used as favorable deposition forming means for production of various electron devices. For example, they are utilized in formation of a deposited film of hydrogenated amorphous silicon (hereinafter referred to as xe2x80x9ca-Si:Hxe2x80x9d) for electrophotography, or the like, and various systems for them have been also proposed heretofore.
It is possible to perform desired vacuum processing or to form a deposited film with desired characteristics by use of the systems proposed heretofore. For a vacuum processing method including the steps of preparing a vacuum processing system constructed of a reaction vessel and an exhauster separable from each other, connecting the reaction vessel to the exhauster for every lot, and thereafter carrying out vacuum processing, there are also proposals of apparatus having both high system operation efficiency and flexibility in production. Utilizing this advantage, improvement has been vigorously made recently, particularly, in vacuum processing methods suitable for multi-product production.
However, the market demand level has been becoming higher day after day, not only for the improvement in productivity, but also for the performance of products made by such vacuum processing methods. In order to meet this demand, therefore, there is a continuing need for development of a vacuum processing method that permits production of products with higher quality and that has a high productivity.
For example, in the case of the electro-photographic photosensitive members produced by plasma CVD, since digital, electrophotographic systems and color electrophotographic systems under spectacular spread in recent years are frequently operated to make copies of photographs, pictures, design graphics, etc. and output images, as well as letter documents, the demand level is very high for the quality of images formed thereby. It is thus of urgent necessity to provide electrophotographic apparatus adaptable for these requirements for high image quality. Technical studies have been done toward improvement in the quality of copied images from various aspects including investigation of the image forming process itself, and among others, the improvement in the characteristics of the photosensitive members for electrophotography is an inevitable subject. For accomplishing this subject, there are strong demands for achievement of a method of forming a photosensitive member for electrophotography capable of achieving improvement in vacuum processing characteristics and also capable of maintaining a high non-defective unit percentage (simply referred to as xe2x80x9cnon-defective percentagexe2x80x9d), based on stable processing characteristics.
Under such circumstances, it is the present status that the conventional vacuum processing methods described above are still susceptible to improvement. In the vacuum processing method using the vacuum processing system in the structure wherein the reaction vessel and exhauster are separable from each other, as described above, the flexibility of production is improved. In this method, since the reaction vessel is moved with a substrate to be processed being placed inside prior to vacuum processing, there remains the subject of how dust is effectively prevented from attaching onto the substrate during the movement. One of countermeasures against it is a method of, prior to placement of the substrate in the reaction vessel, connecting the reaction vessel to the exhauster and then placing the substrate in the reaction vessel in that state. For adopting this substrate placement method, however, it becomes necessary to employ a new means for carrying the substrate into the reaction vessel while preventing the attachment of dust. Further, the vacuum processing cannot be started during the period between the placement of the substrate and completion of a pressure-reducing step of evacuating the interior of the reaction vessel and the time necessary for this evacuation is not so short, which thus leads to time loss in production tact.
In this vacuum processing method there readily occur variability in the vacuum processing characteristics among lots and thus there remains the subject of how the variability among lots are to be suppressed.
The present invention has been accomplished to solve the above subjects and an object of the invention is to provide a vacuum processing method that permits execution of stable vacuum processing and that permits deposited films to be formed without variability in quality.
Another object of the present invention is to provide a vacuum processing method of moving a vacuum processing vessel having an article placed therein, connecting the vacuum processing vessel to a pressure-reduced space different therefrom, and thereafter carrying out at least one vacuum processing step, which comprises novel means that enables attainment of improvement in non-defective percentage of vacuum-processed articles without degrading the flexibility of production while preventing the attachment of dust onto the articles and that also enables attainment of suppression of the variability of the vacuum processing characteristics among lots.
Still another object of the present invention is to provide a vacuum processing method capable of preventing the attachment of dust onto an article in a step of moving a vacuum processing vessel having the article placed therein and connecting the vacuum processing vessel to a pressure-reduced space different therefrom.
Another object of the present invention is to provide a vacuum processing method that excludes factors to cause the variability in the vacuum processing characteristics among lots and has a step configuration also excellent in the flexibility of production.
According to an aspect of the present invention, there is provided a vacuum processing method which comprises placing an article in a vacuum processing vessel and subjecting the article to at least one vacuum processing step therein with the vacuum processing vessel communicating with a pressure-reduced space different therefrom under reduced pressure,
wherein the vacuum processing vessel has at least a first openable/closable opening,
wherein the pressure-reduced space different from the vacuum processing vessel has at least a second opening,
wherein the communication between the vacuum processing vessel and the pressure-reduced space different therefrom is established when, after closely connecting the first opening and the second opening to each other, the first openable/closable opening is brought into an open state,
wherein for the connection, the vacuum processing vessel having the article placed therein is moved to locate the first opening and the second opening at closely connectable positions, and the first and second openings are connected to each other, and during the movement and connection, the first opening is kept in a closed state and the interior of the vacuum processing vessel is kept in a pressure-reduced state,
wherein, for carrying out the at least one vacuum processing step,
the communication between the different pressure-reduced space and the vacuum processing vessel with their respective openings being connected to each other is established by opening the first opening kept in the closed state during the connection, in a state in which the interior of the different pressure-reduced space is also kept in a pressure-reduced state, and
wherein the internal pressure of the vacuum processing vessel kept in the pressure-reduced state during the movement and connection is set higher than the internal pressure of the different pressure-reduced space kept in the pressure-reduced state, when opening the first opening to establish the communication.
According to another aspect of the present invention, there is provided a vacuum processing method comprising the steps of effecting interconnection and disconnection between the interior of a pressure-reduced vacuum processing vessel and a pressure-reduced space, and subjecting an article housed in the vacuum processing vessel to a vacuum processing, wherein the interconnection is effected in a state such that at least the pressure inside the vacuum processing vessel is higher than the pressure of the pressure-reduced space.
The present invention is based on the results of intensive and extensive research to accomplish the above objects, i.e., based on such finding that it is feasible to accomplish the above objects by, during movement of the vacuum processing vessel having the article placed therein, maintaining the pressure inside the vacuum processing vessel within an appropriate range and connecting the vacuum processing vessel in this state with another pressure-reduced space different therefrom.
The invention will be described hereinafter with examples of a deposited film forming apparatus.
Apparatus and methods of forming a deposited film involve those schematically described below.
FIG. 1 shows an example of vacuum processing apparatus applied to the vacuum processing methods. Namely, FIG. 1 is a view schematically showing one configuration example of the deposited film forming apparatus by RF plasma CVD (hereinafter abbreviated as xe2x80x9cRF-PCVDxe2x80x9d) using a frequency in the RF band as a power supply, specifically, an RF-PCVD system applied to formation of a light-receiving member for electrophotography. The structure of the forming apparatus illustrated in FIG. 1 is as follows.
The RF-PCVD system illustrated in this FIG. 1 is generally comprised of three sections; specifically, a deposition system 2100, a source gas supply system 2200, and an exhaust system (not shown) for evacuating the interior of a reaction vessel 2101. In the deposition system 2100 the reaction vessel 2101 houses a cylindrical substrate 2112, a substrate support 2113 incorporating a heater for heating the substrate, and source gas inlet pipes 2114. Further, a high frequency matching box 2115 is connected to a cathode electrode 2111 making a part of the reaction vessel 2101. The cathode electrode 2111 is electrically insulated from the earth potential by insulators 2120, while the cylindrical substrate 2112 is maintained at the earth potential through the substrate support 2113, thus also serving as an anode electrode. A high frequency voltage can be placed between the cathode electrode 2111 and the cylindrical substrate 2112.
The source gas supply system 2200 has source gas cylinders 2221 to 2226 storing respective gases of SiH4, GeH4, H2, CH4, B2H6, PH3, etc., valves 2231 to 2236, 2241 to 2246, 2251 to 2256, and mass flow controllers 2211 to 2216. Each of the source gas cylinders is connected via a valve 2260 to the gas inlet pipes 2114 inside the reaction vessel 2101.
The formation of a deposited film using the RF-PCVD system illustrated in this FIG. 1 can be carried out, for example, according the following procedures.
First, the cylindrical substrate 2112 is placed in the reaction vessel 2101 and the interior of the reaction vessel 2101 is evacuated by the unrepresented exhaust system (e.g., a vacuum pump). Then, the temperature of the cylindrical substrate 2112 is controlled to a predetermined temperature of 200xc2x0 C. to 350xc2x0 C. by the substrate-heating heater built in the substrate support 2113.
For flowing the source gas for formation of the deposited film from the source gas supply system 2200 into the reaction vessel 2101, for example, the following procedures are carried out.
First, it is confirmed that the valves 2231 to 2237 of the gas cylinders and a leak valve 2117 of the reaction vessel are closed and also that the gas inlet valves 2241 to 2246, outlet valves 2251 to 2256, and auxiliary valve 2260 are opened. Then, a main valve 2118 is opened to evacuate the interior of the reaction vessel 2101 and the interior of gas pipe 2116.
When the reading of a vacuum gauge 2119 reaches about 7xc3x9710xe2x88x924 Pa, the auxiliary valve 2260 and outlet valves 2251 to 2256 are closed.
After that, the valves 2231 to 2236 are opened to introduce the respective gases from the gas cylinders 2221 to 2226 and a pressure of each gas is controlled to a predetermined pressure, e.g., to 2 kg/cm2 by pressure regulators 2261 to 2266. Then, the inlet valves 2241 to 2246 are gradually opened to introduce the respective gases into the mass flow controllers 2211 to 2216.
After completion of the above preparation operation to complete preparation for deposition, each of layers is formed according to the following procedures.
When the cylindrical support 2112 reaches a predetermined temperature, one or some needed out of the outlet valves 2251 to 2256, and the auxiliary valve are gradually opened to introduce predetermined gas from the gas cylinders 2221 to 2226 through the gas inlet pipes 2114 into the reaction vessel 2101. Then, each source gas is regulated to a predetermined flow rate by the mass flow controller 2211 to 2216. On that occasion, the aperture of the main valve 2118 is adjusted so as to control the pressure in the reaction vessel 2101 to a predetermined value while monitoring the vacuum gauge 2119. After the internal pressure becomes stable, the RF power supply (not shown), for example, of the frequency of 13.56 MHz, is set to a desired power to introduce the RF power through the high frequency matching box 2115 and the cathode 2111 into the reaction vessel 2101 whereby glow discharge occurs with the cylindrical substrate 2112 acting as an anode. This discharge energy decomposes the source gas introduced into the reaction vessel and a deposited film comprising prescribed silicon as a matrix is formed on the cylindrical substrate 2112. The formation of the deposited film is carried on for a predetermined time. When the deposited film is formed in a desired thickness, the supply of RF power is stopped and the outlet valves are closed to stop the flow of gas into the reaction vessel, thus terminating the formation of the deposited film.
Similar operation is carried out a desired number of times, e.g., several times, thereby forming deposited films in desired multi-layer structure, e.g., a light-receiving layer.
It is needless to mention that in the production of the deposited films in the multi-layer structure described above, the outlet valves other than those of necessary gases are all closed during formation of each of the layers. In order to prevent the gas utilized in formation of a previous layer from remaining in the reaction vessel 2101 and in the pipe from the outlet valves 2251 to 2256 to the reaction vessel 2101, an operation of closing the outlet valves 2251 to 2256, opening the auxiliary valve 2260, and fully opening the main valve 2118 to evacuate the interior of the system once to a high vacuum, is carried out before formation of a next layer as occasion may demand.
In order to uniformize the film formed, it is also effective to rotate the cylindrical substrate 2112 at a predetermined speed by a driving unit (not shown) during formation of the layers.
Further, it is needless to mention that the gas species and valve operations described above are subject to change according to production conditions of the respective layers.
In addition to the deposited film forming apparatus and forming methods by the RF plasma CVD method using the frequency in the RF band, which have been commonly used heretofore, the VHF plasma CVD (hereinafter abbreviated as xe2x80x9cVHF-PCVDxe2x80x9d) using the high frequency power in the VHF band is drawing attention in recent years. Further, development is also active in formation of various deposited films by this VHF plasma CVD method. The reason is that the VHF-PCVD method has the advantages of a high film deposition rate and capability of providing the deposited film with high quality and is thus expected as means capable of simultaneously attaining cost reduction and high quality of products. For example, U.S. Pat. No. 5,534,070 (Japanese Patent Application Laid-Open No. 6-287760) discloses the apparatus and method that are applicable to formation of a-Si based light-receiving members for electrophotography.
In addition, development is also under way to develop a deposited film forming apparatus capable of housing a plurality of substrates, as illustrated in FIGS. 2A and 2B, which permits simultaneous formation of a plurality of light-receiving members for electrophotography and which has an extremely high productivity.
FIGS. 2A and 2B are views showing one configuration example of the deposited film forming apparatus capable of housing a plurality of substrates, in which FIG. 2A is a schematic, sectional view and FIG. 2B a schematic, sectional view along a cut line 2Bxe2x80x942B of FIG. 2A.
An exhaust duct 311 is integrally formed on a side face of a reaction vessel 301 and the other end of the exhaust duct 311 is connected to an exhaust system (not shown). Six cylindrical substrates 305 to be subjected to the formation of a deposited film are placed in parallel to each other so as to surround the central part of the reaction vessel 301. Each cylindrical substrate 305 is held on a rotation shaft 308 and is arranged to be heated by a heater 307. When each motor 309 is actuated, the rotation shaft 308 is rotated via a reduction gear 310, so that the cylindrical substrate 305 rotates about the center axis along the direction of a generator thereof.
Source gases are supplied through a source gas supply means 312 into a deposition space 306 surrounded by the six cylindrical substrates 305. The VHF power is supplied from a VHF power supply 303 via a matching box 304 and a cathode electrode 302 to the deposition space 306. In this system, the cylindrical substrates 305 are also maintained at the earth potential through the rotation shafts 308 and thus act as anode electrodes.
The formation of deposited films using this system illustrated in FIGS. 2A and 2B, is carried out according to the procedures schematically described below.
First, the cylindrical substrates 305 are placed in the reaction vessel 301 and the interior of the reaction vessel 301 is evacuated through the exhaust duct 311 by the unrepresented exhaust system. Then, the cylindrical substrates 305 are heated and controlled to a predetermined temperature of about 200xc2x0 C. to 300xc2x0 C. by the heaters 307.
When the cylindrical substrates 305 reach the predetermined temperature, the source gas is introduced through the source gas supply means 312 into the reaction vessel 301. After it is confirmed that the flow rate of the source gas reaches a set value and the pressure in the reaction vessel 301 becomes stable, the predetermined VHF power is supplied from the high frequency power supply 303 via the matching box 304 to the cathode electrode 302. This places the VHF power between the cathode electrode 302 and the cylindrical substrates 305 also serving as anode electrodes, whereby glow discharge occurs in the deposition space 306 surrounded by the cylindrical substrates 305. This glow discharge excites and dissociates the source gas to form deposited films on the cylindrical substrates 305.
After formation of the films in a desired thickness, the supply of the VHF power is stopped and the supply of the source gas is also stopped, thereby ending the formation of deposited films. Like operation is carried out several times to form deposited films in desired multi-layer structure, e.g., light-receiving layers.
During the formation of deposited films the cylindrical substrates 305 are rotated at a predetermined speed through the rotation shafts 308 by the motors 309 whereby the deposited films are formed across the entire periphery of the surfaces of the cylindrical substrates. In addition, this uniformizes the deposited films obtained.
Japanese Patent Application Laid-Open No. 8-253865 discloses the technology of simultaneously forming deposited films on a plurality of substrates by use of plural electrodes. It describes that the simultaneous formation of the deposited films on the plural substrates by use of the plural electrodes permits attainment of effects of improving the productivity and of improving uniformity of characteristics of deposited films. The formation of deposited films in this form can be realized, for example, by use of a system having the structure as illustrated in FIGS. 3A and 3B.
FIGS. 3A and 3B show an example of apparatus employing a method of simultaneously forming deposited films on plural substrates by use of plural electrodes, in which FIG. 3A is a schematic, vertical, sectional view and FIG. 3B a schematic, horizontal, sectional view. An exhaust duct 405 is integrally formed on a top surface of a reaction vessel 400 and the other end of the exhaust duct 405 is connected to an exhaust system (not shown). Inside the reaction vessel 400, a plurality of cylindrical substrates 401 to be subjected to the formation of deposited films are placed in parallel to each other. Each cylindrical substrate 401 is held on a shaft 406 and is arranged to be heated by a heater 407. Each cylindrical substrate 401 is rotated through the shaft 406 by a driving means such as a motor or the like (not shown), as occasion may demand.
The VHF power is supplied from a VHF power supply 403 via a matching box 404 and cathode electrodes 402 into the reaction vessel 400. In this system, the cylindrical substrates 401 are also maintained at the earth potential through the shafts 406 and thus act as anode electrodes.
Source gases are supplied through unrepresented source gas supply means set in the reaction vessel 400, into the reaction vessel 400.
The formation of deposited films by use of this system in the structure illustrated in FIGS. 3A and 3B can also be carried out according to similar procedures to those by the deposited film forming system described above referring to FIGS. 2A and 2B.
Meanwhile, a wide variety of products are made today by making use of such vacuum processing systems and vacuum processing methods and different vacuum processing systems are often used depending upon the various products. This diversity results from application of vacuum processing systems of sizes, materials, etc. optimal to respective types of products. For example, in the case of production of photosensitive members for electrophotography, it is sometimes necessary to change the vacuum processing systems used, more specifically, the dimensions of the deposited film forming apparatus, particularly, the cathode sizes, according to the diameters of the electrophotographic, photosensitive members to be produced.
Under the circumstances of the increasing diversity of products to be produced, when the products are made using the vacuum processing system consisting of the aforementioned reaction vessel and exhauster substantially integrated with each other, a new production line also including another exhauster must be added in order to newly produce different products, or an existing production line must be modified to replace the existing reaction vessel with a new reaction vessel. Naturally, new equipment investment becomes necessary for the addition of the new production line. For replacing the existing reaction vessel with a new reaction vessel, the equipment investment is lower, but production efficiency also becomes lower, because the production line cannot be used during the modification.
Further, in order to produce the conventional products and new products in parallel, individual production lines have to be prepared. If there will be change in necessary numbers of respective products in future, conversion of the systems will be implemented by modification, but the modification will require a considerable time, thus failing to adjust the ratio of numbers of production lines instantly.
For the purpose of quickly implementing the conversion of apparatus, attention is recently focused on a type in which the vacuum processing apparatus is constructed of the reaction vessel and exhauster separable from each other and in which a reaction vessel optimal for necessary products is connected to the exhauster to perform vacuum processing, according to a production plan. This type of the disconnectable configuration of the reaction vessel and exhauster has high flexibility in production and makes it feasible to achieve increase of production efficiency and decrease of production cost. In this disconnectable system configuration, where the reaction vessel is arranged movable, the loading of the substrate into the reaction vessel in the preparation step can be carried out by moving the reaction vessel to a stage for substrate loading. Accordingly, the reaction vessel in the fixed structure required use of a large-scale substrate carrier in order to carry and load the substrate into each reaction vessel, whereas the reaction vessel in the movable structure obviates the need for use of the large-scale substrate carrier and permits simplification of the production system.
Therefore, the method of constructing the vacuum processing apparatus of the reaction vessel and exhauster separable from each other, connecting the reaction vessel suitable for necessary products to the exhauster, and then performing vacuum processing, has many merits and is thus drawing particular attention in recent years.
The schematic structure of the system comprised of the reaction vessel and exhauster in the separable configuration is, for example, one as illustrated in an example of FIG. 4. FIG. 4 shows an example of the structure in which the reaction vessel and exhauster are separable from each other and, particularly, in which the reaction vessel is movable. Numeral 501 designates a movable reaction vessel section, which consists of a reaction vessel 506, a vacuum seal valve 508, a connection flange 504, and a carriage 513 on which the reaction vessel 506 is mounted, thereby permitting movement thereof. Numeral 502 denotes an exhaust section, which consists of an exhaust means 507, a vacuum seal valve 509, and a connection flange 505. Numeral 503 represents a connection section for connection between the reaction vessel section 501 and the exhaust section 502.
The structure inside the reaction vessel 506 can be constructed, for example, in the structure as illustrated in FIGS. 5A and 5B. FIGS. 5A and 5B are schematic views showing an example of the reaction vessel section in the deposited film forming apparatus for forming the photosensitive members for electrophotography. FIG. 5A is a schematic, sectional view and FIG. 5B a schematic, sectional view along a cut line 5Bxe2x80x945B of FIG. 5A.
An exhaust duct 611 is formed on a side face of a reaction vessel 601 and the other end of the exhaust duct 611 is connected to the vacuum seal valve 508 in FIG. 4. An unrepresented conductive mesh is set in the opening of the exhaust duct in order to prevent leakage of a high frequency power guided into the reaction vessel, to the exhaust means side. Cylindrical substrates 605 to be subjected to the formation of deposited films are placed at equal intervals and in parallel to each other on a common circle. Each substrate 605 is held on a rotation shaft 608 and a motor 609 connected thereto is actuated to rotate the rotation shaft 608 through a reduction gear 610, whereby the cylindrical substrate 605 rotates about the center axis along the direction of a generator thereof. The cylindrical substrates 605 can be heated by respective heaters 607.
The high frequency power outputted from a high frequency power supply 603 is supplied through a matching box 604 and a high frequency power supply cable 615 and via cathode electrodes 602 into the reaction vessel 601 serving as a deposition space. A cathode electrode 606 is also placed inside the placement circle of the cylindrical substrates 605 and the high frequency power outputted from a high frequency power supply 614 is supplied through a matching box 613 and a high frequency power supply cable 615 and via the cathode electrode 606 into the reaction vessel 601.
Source gas supply means 612 are placed inside the reaction vessel 601 and desired source gas is supplied therethrough into the reaction vessel 601.
The vacuum processing using the vacuum processing system illustrated in the example of FIG. 4 can be carried out according to the procedures schematically described below, for example, when the reaction vessel of the movable type is the deposition forming reaction vessel for formation of photosensitive members for electrophotography shown in the example of FIGS. 5A and 5B.
First, the movable reaction vessel section 501 is disconnected from the exhaust section 502, the connection flange 504 is connected to another exhaust system for loading of substrates (not shown), and in the thus connected state cylindrical substrates 605 are loaded into the reaction vessel 601. Then, the interior of the reaction vessel 601 is evacuated through the exhaust duct 611 by the exhauster for loading of substrates. It is needless to mention that the exhaust seal valve 508 is opened during this evacuation period. After the interior of the reaction vessel 601 is evacuated to a desired pressure, the vacuum seal valve 508 is closed and then the connection flange 504 is disconnected from the substrate-loading exhauster. Then, the movable reaction vessel section 501 is moved to the placement site of the exhaust section 502 and the connection flange 504 is brought into contact with the exhaust-side connection flange 505 through a vacuum seal and connected therewith. After the connection, the connection section 503 is fixed by fixing means such as screws, clamps, etc. as occasion demands.
After it is confirmed that the movable reaction vessel section 501 is connected to the exhaust section 502, the exhaust-side vacuum seal valve 509 is first opened, the interior of the pipe on the exhaust means 507 side with respect to the reaction-vessel-side vacuum seal valve 508 is evacuated by the exhaust means 507, and the reaction-vessel-side vacuum seal valve 508 is then opened to evacuate the interior of the reaction vessel 506.
This preparation step, i.e., the stage of loading the substrates into the reaction vessel 506, the stage of moving the reaction vessel section 501, and the stage of connecting the reaction vessel section 501 to the exhaust section 502, may also be carried out, for example, according to procedures of loading the substrates, thereafter moving the reaction vessel section 501 without evacuating the interior of the reaction vessel 506, and then connecting the reaction vessel section 501 to the exhaust section 502, different from the procedures described above. With those different procedures, a necessary condition is that evacuation is completed in the reaction vessel 506 etc. to establish a processable state before a start of an actual vacuum processing step with the reaction vessel section 501 being connected to the exhaust section 502. Accordingly, specific procedures in this preparation step can be adequately determined in consideration of work efficiency, productivity, etc. in each of production steps.
After the interior of the reaction vessel 506 is evacuated by the exhaust means 507 in this way, the cylindrical substrates 605 are heated and controlled to a predetermined temperature by the heaters 607 as occasion demands. When the cylindrical substrates 605 reach the predetermined temperature, the source gas is introduced through the source gas supply means 612 into the reaction vessel 601. After it is confirmed that the flow rate of the source gas reaches a set flow rate and the pressure inside the reaction vessel 601 becomes stable, the predetermined high frequency power is supplied from the high frequency power supplies 603, 614 via the matching boxes 604, 613 to the cathode electrodes 602, 606. The high frequency power thus supplied Induces glow discharge in the reaction vessel 601 and the glow discharge excites and dissociates the source gas, whereby deposited films are formed on the cylindrical substrates 605.
After the e deposited films are formed in a de sired thickness, the supply of a high frequency power is stopped and the supply of source gas is also stopped, thus terminating the formation of deposited films. For forming the deposited films in the multi-layer structure, similar operation is repeated several times. In this case, the multiple layers may be formed according to procedures of completely terminating discharge once at the time of completion of formation of one layer as described above, between two layers, changing the setting to a gas flow rate and a pressure for a next layer, and thereafter again inducing discharge to form the next layer, or the multiple layers may be continuously formed according to procedures of, after completion of formation of one layer, gradually varying the gas flow rate, pressure, and high frequency power to set values for the next layer in a fixed period.
During the formation of deposited films, the cylindrical substrates 605 are preferably rotated through the rotation shafts 608 at a predetermined speed by the motors 609 as occasion may demand. By rotating the cylindrical substrates 605, the deposited films are formed under the same conditions across the entire periphery of the surfaces of the cylindrical substrates, thus achieving better uniformization of the deposited films obtained.
After completion of the deposited film forming step in this way, the source gas in the reaction vessel 506 is adequately purged or preferably replaced with inert gas, and thereafter the vacuum seal valves 508, 509 are closed. Then, the connection section 503 is disconnected to bring the reaction vessel section 501 into the movable state. In this state, the reaction vessel section 501 is moved to a substrate unloading site.
As occasion may demand, the substrates 605 are cooled to a desired temperature, and thereafter an inert gas or the like is introduced via an unrepresented leak valve into the reaction vessel 506, so as to bring the interior of the reaction vessel 506 into the atmospheric pressure. After the interior of the reaction vessel 506 reaches the atmospheric pressure, the substrates 605 with the deposited films thereon are taken out of the reaction vessel 506.
After that, the components in the reaction vessel 506 are subjected to replacement, cleaning, etc. to recover the reaction vessel 506 into a state in which the deposited films can be formed again. Then, the reaction vessel 506 is again subjected to the aforementioned substrate loading procedure.
In the vacuum processing operation of carrying out the three divisional steps of substrate loading, formation of deposited films, and substrate unloading at the respective, separate sites, it is preferable in terms of efficiency to prepare and use a plurality of reaction vessel sections 501. Namely, in the series of steps described above, at the stage when, after completion of formation of deposited films with a reaction vessel section 501 connected to the exhaust section 502, the reaction vessel section 501 is disconnected from the exhaust section 502, another reaction vessel section 501 already having passed through the preliminary preparation step of substrate loading is connected to the exhaust section and the step of formation of deposited films can be started subsequent thereto. This decreases a wait time and permits efficient operation as a whole of the apparatus.
The above described the examples of the apparatus and methods of forming the electrophotographic, photosensitive members, and it is noted that similar techniques can also be applied to other vacuum processing steps, e.g., etching, ion implantation, etc., or to other vacuum processing methods, e.g., sputtering, thermal CVD, etc., in addition to the above.
The above-stated conventional methods can be used to perform the vacuum processing with desired characteristics, for example, to form the deposited film well. Among others, the method employing the vacuum processing system in the separable configuration of the reaction vessel and exhauster and carrying out the vacuum processing after connection of the reaction vessel to the exhauster for every lot, has the flexibility in production, in addition to the high system operation efficiency. Utilizing this advantage, improvement has been energetically made particularly in recent years, as a vacuum processing method suitable for multi-product production.
However, as described previously, there are demands for further improvement in the performance of products made by this vacuum processing method, as well as improvement in productivity, in recent years, so that the market demand level is becoming higher day after day. Accordingly, there are desires for development of a vacuum processing method that permits the production of products with high quality and that has a high productivity, in order to meet the above demand.
For example, in the case of the electrophotographic, photosensitive members produced by the plasma CVD method, not only the letter documents, but also graphics including photographs, pictures, design images, etc. are frequently copied in the recently quickly spreading, digital, electrophotographic systems and color electrophotographic systems and thus the demand level for the quality of copied images is becoming very high, e.g., much higher resolution, high quality of output of halftone images like photographs, suppression of variability among photosensitive members or variability in characteristics in one photosensitive member, which can be the cause of irregular color or chromatic deviation with formation of color images, and so on. It is thus of urgent necessity to provide the electrophotographic apparatus adaptable for these demands for high image quality. Technological studies toward improvement in quality of copied images has been conducted from various aspects including the research of image forming process itself, and among others, the improvement in the characteristics of the photosensitive members for electrophotography is an essential subject. For accomplishing this subject, there are strong needs for attainment of the method of forming the photosensitive member for electrophotography, which can accomplish the improvement in the characteristics of vacuum processing and which is also stable in the processing characteristics to be able to maintain a high non-defective percentage. Then, there are earnest hopes for the vacuum processing method capable of producing the electrophotographic, photosensitive members with such high quality on a stable basis.
The present invention has been accomplished in view of this point and with focus on such knowing that, on the occasion of carrying out the vacuum processing by use of the processing system in which the vacuum processing vessel can be moved with the article being placed in the vacuum processing vessel, the pressure in the vacuum processing vessel is controlled in the appropriate range and in this state the vacuum processing vessel is connected to another pressure-reduced space different therefrom, whereby the vacuum processing, e.g., formation of a deposited film of a semiconductor or the like, can be performed at extremely high efficiency and with extremely high quality.
Namely, a vacuum processing method of the present invention is a vacuum processing method in which, in a state where an article is placed in a vacuum processing vessel and where under reduced pressure the vacuum processing vessel communicates with another pressure-reduced space different therefrom, the article is subjected to at least one step of vacuum processing steps, wherein the vacuum processing vessel comprises at least a first openable/closable opening; the pressure-reduced space different from the vacuum processing vessel comprises at least a second opening; the communication between the vacuum processing vessel and the pressure-reduced space different therefrom is established on the occasion of, after close connection between the first opening and the second opening, bringing the first openable/closable opening into an opened state; during execution of the connection, the vacuum processing vessel with the article being placed therein is moved to a position where the first opening and second opening can be closely connected to each other, and the openings are then connected; during execution of the movement and connection, the first opening is kept in a closed state and the interior of the vacuum processing vessel is kept in a pressure-reduced state; during execution of at least one step of the vacuum processing steps, the communication between the pressure-reduced space and the vacuum processing vessel with their openings being connected to each other is established by opening the first opening kept closed during the connection, while the interior of the pressure-reduced space is also kept in a pressure-reduced state; an internal pressure of the vacuum processing vessel kept in the pressure-reduced state during the movement and connection is set higher than an internal pressure of the pressure-reduced space kept in the pressure-reduced state, on the occasion of opening the first opening to establish the communication.
In the vacuum processing method of the present invention, it is desirable to set the internal pressure of the vacuum processing vessel kept in the pressure-reduced state during the movement and connection, preferably to not more than 1xc3x97103 Pa and more preferably to not more than 1xc3x97102 Pa.
On the other hand, when P1 [Pa] and P2 [Pa] represent the internal pressure of the vacuum processing vessel in the pressure-reduced state and the internal pressure of the pressure-reduced space in the pressure-reduced state, which are made to communicate with each other by opening the first opening after the connection, a difference between P2 and P1 preferably satisfies the following relation on the occasion of the communication:
P1xe2x88x92P2xe2x89xa70.1 Pa.
Further, the difference between P2 and P1 preferably satisfies the following relation on the occasion of the communication:
xe2x80x83P1xe2x88x92P2xe2x89xa71 Pa.
In addition, the vacuum processing method of the present invention preferably comprises an operation of varying exhaust resistance between the pressure-reduced space and the vacuum processing vessel communicating with each other, after the first opening is opened to establish the communication. On that occasion, the exhaust resistance between the pressure-reduced space and the vacuum processing vessel communicating with each other is preferably decreased continuously or stepwise after the first opening is opened to establish the communication.
In the vacuum processing method of the present invention, the at least one of the vacuum processing steps, which is performed on the article with the pressure-reduced space and the vacuum processing vessel communicating with each other, may comprise a deposited film forming step. In this case, the deposited film forming step as the at least one of the vacuum processing steps may comprise a step of forming a deposited film having a plurality of regions different at least in composition. For example, the vacuum processing steps comprising the deposited film forming step as at least one step thereof are preferably formation of a deposited film for producing an electrophotographic photosensitive member.